Tags in the questions should follow the official standard for Web 2.0 tags. This means that all tags should have rel="tag" attribute. See the official specification http://microformats.org/wiki/rel-tag. You could also look the way WordPress implements tags, e.g. here.

You are right: at this forum the tags are implemented correctly. I see the rel="tag" attribute. But I have another instance where the tags are not behaving correctly.

We performed a standard install of the 1.5 version of the question2answer here: http://forums.academy.telerik.com. The rel="tag" attribute in the tags at our instance of q2a is missing. Do you know where the problem comes from? We just performed a standard install and we use the default skin. We just added few plugins (like facebook login + wysiwyg editor, etc.)